This invention relates to a particle color discriminating apparatus comprising a vibration feeder for feeding particles to be discriminated, a shooter for causing the particles to flow downwardly in a stream of a predetermined locus, photoelectric detecting means located in the vicinity of the path of flow of the particles from the shooter for detecting particles distinct in color from the particles of interest (hereinafter referred to as particles of dissimilar colors), an air ejector arranged beneath the photoelectric detecting means, and control means for controlling actuation of the air ejector in accordance with an output signal of the photoelectric detecting means for separating the particles of dissimilar colors by the action of air blasts from the air ejector, and more particularly to an automatic control device for the particle color discriminating apparatus of the type described.
In this type of particle color discriminating apparatus of the prior art, such as grain particle color discriminating apparatus, when the proportion of foreign matter incorporated in the grain particles suddenly increases, the foreign matter flows substantially continuously and the operation of the apparatus is thrown into confusion so that the precision with which discrimination is effected is lowered, because there are limits to the operation time of the discriminating apparatus including the photoelectric detecting means and air ejector in handling the same flow rate of particles when the proportion of foreign matter incorporated in the particles becomes high as when it is low. Therefore, the apparatus of the prior art is provided with a control circuit for producing a signal for interrupting the operation of the vibration feeder in such critical conditions. The apparatus of the prior art has had the disadvantage that it is shut down unnoticed and the apparatus is kept inoperative without any attention being given to its failure.